384 bulletin: museum of compakative zoology. 



wished to see more material from British America, from the states of 

 Kentucky, Tennessee, Alabama, and Mississippi and from the moun- 

 tains of Northern Mexico, These are regions in which, unfortunately, 

 very few ants have been collected. 



Formica, Lasius, Stenamma, and Myrmica are the only circum- 

 polar genera that are confined to the Northern hemisphere. Of these 

 Formica is the most eurythermal, ranging in Europe, Asia, and North 

 America from a latitude of 30° to 60° or 65°, and therefore nearly to 

 the Arctic circle.^ In altitude the species range from sea-level to 

 above timberline on our loftiest mountains (12,000 to 12,500 ft.). 

 The species of both Lasius and Myrmica are more stenothermal, as 

 they spread neither so far north nor so far south, nor to such alti- 

 tudes. In passing I may note that I have seen no specimens of 

 Formica from Florida although I have studied many collections of 

 ants from that state. The single species known to me from Mexico 

 (F. pcrpilosa) occurs only on the high plateau. In all probability a few 

 other forms, such as F. gnava and F. pilicornis, will eventually be 

 found in the same region. 



The various species, subspecies, and varieties of Formica differ 

 considerably in habitat. Thus F. pallidefulva sens, sir., vioki, inli- 

 cornis, perpilosa, and the various forms of rufibarbis are so decidedly 

 xerothermal that they are confined to rather arid portions of the upper 

 and lower austral zones in the southern and southwestern states, 

 whereas the typical fusca and its varieties subacncsccns, marcida, and 

 gelida, F. sanguinea subnuda and F. ulkei are essentially boreal or 

 subalpine and properly belong to the Canadian and Hudsonian zones. 

 The majority of the species, however, are characteristic insects of 

 Merriam's transition zone. 



Practically all of the species find their optimum environment in 

 hilly or mountainous country at moderate elevations, where there 

 are open woods and thickets of deciduous or mixed trees and shrubs, 

 where the rain-fall is abundant and there is nevertheless plenty of 

 heat and sunshine during the summer months, and where, owing to the 

 sloping surface of the soil and abundance of stones, the land is neither 

 flooded nor parched during certain periods of the year. Hence we find 

 the species of Formica most conspicuously abundant and their colo- 

 nies most numerous and populous in the mountain regions of both 



1 Kolbe (Glazialzeitliche reliktenfauna im hohen norden. Deutschr. ent. zeitschr., 

 1912, p. 33-63) mentions Formica (presumably F. fusca) as occurring even as far north 

 as 67° 34' at Werchojansk on the Jana River in the province of Irkutsk, Siberia. This 

 is said to be one of the coldest spots on the planet, with a minimum temperature of 

 -60° to -67° C. 



